Automatic shaft positioning apparatus



April 6, 1955 E. E. JONES ET AL 2,707,041

AUTOMATIC SHAFT POSITIONING APPARATUS Filed Feb. 19. 1949 INVENTORS waagmw x @VEST AGENT 2,707,041 Patented Apr. 26, 1955 2,707,041 AUTDMATHCSHAFT PQSITEONING APPARATUS Eric E. Jones, Courtlands, Richmond,England, and Willlelmus Lambertus Vervest, Eindhoven, Netherlands,assignors to Hartford National Bank and Trust Company, Hartford, Comm,as trustee Application February 19, 1949, Serial No. 77,424

Claims priority, application Netherlands February 23, 1948 5 Claims.(Cl. 192142) This invention relates to a shaft-positioning device, andmore particularly to a shaft-positioning device which includes a pawlknob.

A pawl knob is a system of associated locking discs and pawls whichpositions, for example, the shaft serving to control the capacity of acondenser in a transmitter or a receiver for wireless intelligence or toadjust other tuning members. With the use of pawl knobs control-membersmay be readily moved from one position to another. Furthermore,apparatus comprising pawl knobs are adapted to be operated by remotecontrol.

For each position of the shaft required to be selected the pawl knobcomprises a locking disc and an associated pawl. A movable selectingmember, which is referred to as a pawl selector, permits any selectedpawl to be caused to co-operate with the locking disc with which it isassociated.

A number of such pawl knobs, each of which operates on a separate shaftmay be assembled to form a mechanism in which the shafts are adapted tobe operated by a common driving arrangement either by hand or with theuse of a motor.

A device is known in which the pawl selector of a pawl knob is displacedby the same operating device knob shaft is rotated during the secondstep until it is locked by the operative pawl upon reaching the selectedposition.

Initially, the present device was constructed so that the direction ofrotation of the driving shaft had to be reversed with the use of acontrol-knob. The attention of the operator was required to perform thisoperation at the correct time.

In an alternative embodiment the direction of rotation is reversedautomatically.

ary contact members. Each stationary contact member is associated with adefinite pawl. The contact arm of this position switch is movedsimultaneously with the pawl selector, so that each position Thiscurrent may, for example, serve as the controlcurrent of a relay, theswitch of which reverses the field current of a motor which actuates thedriving shaft.

This device has also a limitation. As soon as the contact arm hascontacted the selected contact member, it stops moving. If the contactarm moves excessively slowly, the contact surface between the contactarm and the stationary contact member will be small so that the contactis unreliable. It will readily be interrupted due to vibration or toimpurities (burning). This phenomenon occurs particularly if themovement of the drivretardation, as is generally the case of electricdriving. If, on the contrary, the pawl selector and the contact arm movewith excessive speed, the contact arm may pass over the selected contactmember before the closing current has any effect. Consequently, thisdevice requires a quite defined ratio between transmission of themovements from the driving shaft to the pawl selector and the contactarm.

The invention relates more pawl knobs and a common driving arrangementfor the pawl selector and the shaft of are not inherent.

According to the invention, the separating device of the pawl selectorand the pawl selector itself have arranged between them a lockingelement.

equal to the number of pawls of the pawl knob. locking positions a pawlis caused to co-operate with the pawl disc with which it is associated.

The locking element may be formed by a pawl wheel and a pawlco-operating therewith and The pawl wheel of the plawl selector. Foreach SiEnilarly to the known devices, the device according to t eseparating device being, for example, a simple ratchetgear coupling (aone-way coupling) similar to the above known devices.

However, mechanical locking of the pawl selector enables a moreefficient method tional ratchet-gear coupling.

In order thatthe invention may be more clearly underpawl knob, pawlknobs may be assumed to be and an operative .by like referenceCorresponding parts are designated in Figs. 1 and 2 numerals.

The two devices shown each comprise a motor 1 which serves to drive thepawl selector as well as the shaft of the pawl knob. They aredifferentiated in that in the device shown in Fig. 2 the motor isautomatically stopped when upon changing their positions all the pawlknobs occupy their new positions, and in the device shown in Fig. 1 theswitch of the motor is operated manually.

Referring more particularly to Fig. 1, motor 1 drives a gear wheel 2,which meshes with two further gear wheels 3 and 4. Actuated through gearwheel 3 is a shaft 5 on which are seated pawl selectors 6, 7 and 8, themovement being transmitted from gear wheel 3 to the shaft 5 through ashaft 9, a separating device 10 and a set of bevel gears 11.

Driven through gear wheel 4 is a shaft 12, the movement of which istransmitted with the use of a set of bevel gears 13, 14 and 15 to shafts16, 17 and 18 respectively.

In line with the pawl knob shafts 16, 17 and 18 are shafts of controlmembers which are operated with the use of the pawl knobs and all ofwhich are actuated at a time by the motor 1. Said control members arenot shown.

A system of locking discs is clamped to the shaft of each pawl knob.Each system comprises the same number of discs, for example eightpieces. The drawing shows a single locking disc (19, 20, 21) for eachpawl knob and a single rotatable pawl (22, 23, 24) for each pawl knob,but in actual fact each locking disc is associated with such a pawl.

When a pawl is caused, by the pawl selector 6, 7, 8 to co-operate withthe locking disc and the latter is actuated, the edge of the disc passesalong the pawl until a notch in the disc has reached the pawl. The pawl,which is urged by a stressed spring (25, 26, 27) snaps into the saidnotch and prevents further rotation of the disc system and hence of thecontrol shaft.

As a rule, all of the pawl knob shafts will not reach the lockingposition at the same time. Thus, for example, when they rotate in thedirection denoted by an arrow at the locking disc 19, the hooked end ofthe pawl 22 will snap into the notch 28 in the locking disc 19 when thenotches 29 and 30 are still remote from the pawls 23 and 24respectively.

For this reason provision is made between the driving shaft 12 on theone hand and the pawl knob shafts 16, 17 and 18 on the other hand ofoverload couplings 31, 32 and 33, which enable the shaft 12 to continueits rotation when one or more pawl knob shafts are locked.

For this purpose use may be made of a friction clutch or with advantageof an overload coupling of the kind in which the driven shaft iscompletely separated in the case of overload and due to resilient meansoperative between the driven shaft and a locking member remains underthe influence of a driving torque. Such an overload coupling isdescribed, for example, in French specification 903.072.

Thus, on the shaft 16 of the device shown in Fig. 1 being locked by pawl22 it is separated by the overload coupling 31. Shaft 12 continues torotate and this movement is followed by the pawl knob shafts 17 and 18.Not until disc 21 has rotated through a larger angle than disc 19 doesits notch register with pawl 24 and is it locked in turn. The shaft 18is then also separated and it is only shaft 17 which continues to rotatebut is locked upon the notch 29 in locking disc reaching pawl 23.Thereupon shaft 17 is also separated and the change in position of thecontrol-members is completed.

The co-operation of the pawls with the pawl selector is illustrated inthe figure in that the pawls 22, 23 and 24 are lengthened on the otherside of their points of rotation by an arm (34, 35 and 36) which bearson the edge of the pawl selector.

The shafts of the pawl knob and the pawl selector may be in line withone another and in this case the arm of the pawl may be secured to arotatable shaft which also supports the pawl and is arranged parallel tothe pawl knob shaft, the arms of all the pawls being in one plane atright angles to the shaft and the pawls themselves being located indifferent planes, the shafts of the pawls forming the edges of anequilateral prism.

On the pawl selectors being rotated by the shaft 5, the edges of thepawl selectors pass along the arms of the pawls. The periphery of a pawlselector is circular for the major part but for a small part itcomprises a recess (37, 38, 39). On this recess registering with the armof a pawl, the end of the arm moves into it under the influence of aspring (25, 26, 27) without the pawl selector becoming locked. The endof the pawl adjacent the locking disc is then urged by the springagainst the edge of this disc. The angle through which the recess (37,38, 39) extends need not have an accurately defined value but must besmaller than n being the number of pawls.

If the pawl knobs are required to change their positions the shaft 5must be caused to turn and be locked when the recess (37, 38, 39) of thepawl selector registers with the arm of the pawl concerned. The drawingshows the pawl selectors occupying positions in which the arms 34, 35and 36 are about to move into the recesses of the pawl selectors.

On the shaft 5 starting to rotate, first the pawl of each pawl knobwhich hitherto was operative is ejected, so that the arrangement forlocking discs start to move, the couplings 31, 32 and 33 transmittingthe movement from the shaft 12 to the shafts 16, 17 and 18.

In order to lock the pawl selectors provision is made of a lockingelement comprising an electro-magnetically operated pawl (selector pawl)49 and a pawl wheel 41, which is firmly seated on the pawl selectorshaft 5. This locking element is controlled by a position selector 42.The latter comprises a movable contact arm 43 and as many stationarycontact members as there are locking positions of the pawl selector. Inthe embodirnent shown by way of example this number is 8. The stationarycontact members are designated I to VIII. They are electricallyconnected to the corresponding stationary contact members I to Vlll of aposition switch 44, the movable contact member of which is secured tothe pawl selector shaft 5. The electric connections may have any length,so that the position selector 42 may be remote from the position switch44 and the pawl knob mechanism.

Fig. 1 shows the movable contact member of the position switch and itscontact arm 45 which cannot contact periodically with more than onestationary contact member of this switch. In this figure the contact armof the position selector 42 is moved into position I. On the current ofthe motor I being started with the use of a manual switch 46, the shafts12 and 5 are set rotating and thus the contact arm 45. As soon as thiscontact arm contacts the stationary contact member I, as shown in Fig. 1to have been the case immediately before, a circuit is closed. Thecurrent passes in this circuit from one of the terminals 47 of a currentsource (not shown) through the contact arm 43 of the position selector42, the stationary contact member I and then through the stationarycontact member I of the position switch 44 and contact arm 45 and thenceto the coil 48 of an electromagnet 49. From the coil 48 the currentpasses directly to the other terminal 50 of the current source. Theelectromagnet 49 energized by this current attracts its armature 51.This armature is secured to the selector pawl 40 which is thus alsoactuated by the magnet 49 and moved into its active position.

The pawl wheel 41 comprises as many teeth as there are locking discs oneach pawl knob, that is to say eight in the example described. Theselector pawl 40 is shown 111 Fig. 1 to have just dropped on the back ofone of the teeth 52 and engages it. On the pawl wheel 41 has turnedthrough a small angle a, the front of the next following tooth 53 abutsagainst the selector pawl 40 and the pawl wheel, and hence also theshaft 5 with the pawl selectors 6, 7 and 8 are locked. At the momentwhen, this occurs, contact arm 45 is midway on the stationary contactmember I, so that an adequate contact is maintained and the doubled overends of the arms 34, 35 and 36 engage the recesses 37, 38 and 39 of thepawl selectors 6, 7 and 8.

The device might be constructed so that at this instant the direction ofrotation of the motor is reversed and not until then the pawl knobshafts are thus set rotating, the

separating device 10 being thus enabled to be a condisc 62 is firmlyseated on the driven shaft, thus for exventional ratchet-gear couplingand a coupling of this ample, on the pawl knob shaft 16. The springsmust be kind being also required between the gear wheel 4 andsufiiciently rigid to transmit, without excessive extension, the shaft12. the normal torque from the disc 60 to the disc 62. As the In thedevice according to the drawing, the driving 5 torque increases thesprings are extended to a further arrangement rotates in the samedirection for operating extent, so that the driven shaft slightly lagsbehind the the pawl selectors as for actuating the pawl knob shafts.driving shaft. For this reason the separating device is formed asSecured to the disc 62 is a stud 64 which extends to an overloadcoupling This may be a friction clutch but the front through a slot 65of disc 60 and. which is moved alternatively, use may be made of acoupling of the kind 10 in this slot upon relative movement of thedriven shaft mentioned above as suitable for use with the shafts 16,with respect to the disc 60. For a given extension of 17 and 18. thesprings 63, the stud 64, due to its displacement en- Consequently, eventhough shaft 5 is locked by selecgages the pawl 61 urges it upwatds andforces it to recontlnue to rotate. The locking discs, which have alreadyengaged, the shafts being thus fully separated. This ocstarted to move ashort time after the selectors have curs, for example when in the pawlknobs the shafts 16 come into operation continue this movement untilthey and so forth are locked, while at the same time the shaft arelocked in succession by the operative pawls 22, 23 12 is still rotatingunder the influence of the motor 1.

and 24. Upon locking of all the pawl knobs the motor 1 Upon the shaftsbeing separated the disc 60 is remay be held with the use of switch 46,which may be tracted by the springs 63 and, without further expedients,arranged in the proximity of the position selector 42. For pawl 61 wouldbe released by the stud 64 and the pawl, subsequently changing theposition of the control shafts, which is under spring stress, wouldre-engage the teeth all that needs to be done is to displace the contactarm of the pawl wheel 59. his, however, is prevented by the 43 and toclose the switch 46. The control current of provision of a clampingdevice which prevents retraction the magnet 49 is then interrupted and aspring 54 moves 25 of the disc 60. It comprises a clamping pawl 66formed the selector pawl 40 into its inoperative position. as a rolleror a ball which is arranged in a wedge-shaped In the device shown inFig. 1 the control current of space between the outer surface of disc 60and the inner electromagnet 49 is invariably closed as long as theshafts wall of a ring 67 which surrounds the disc 60. When arestationary. If this is looked upon as inconvenient the springs 63 tendto turn the separated disc 69 in the the locking element may be made tooperate otherwise, direction opposite to the arrow, the pawl 66 isimmedias shown in Fig. 2, the selector pawl being moved into atelyjammed. This prevents the disc 60 from turning the inoperative positionby the energized electromagnet back relatively to ring 67 and the pawl61 remains 49 and into the operative position by the spring 54 andejected. the movable contact member of the position switch being Duringthis time the locked shaft remains subjected to formed into the shape ofa disc or a segment 55 and the maximum couple of driving forces that.can be transcontacting at the same time with all the stationaryconmitted. It is supplied by the springs 63 and the reactive tactmembers but one. The disc comprises a recess 56, force is the clampingforce of the clamping pawl 65 which is shown in Fig. 2 immediately afterhaving reexerted on the ring 67, which constitutes the locking leasedthe stationary contact member I and since the conmember. Consequently,the pawl knob shafts are not tact arm 43 of the position selector 42 hasbeen moved only locked but also fixed in the locking position, so toengage the stationary contact member I the coil 48 of that once aposition is adjusted it remains accurately electromagnet 49 has nolonger any current passing maintained so long as the pawl 22 locks thedisc 19. It through it when this condition prevails In contradistincisdue to this couple of forces, supplied by the springs 63, tron to thedevice shown in Fig 1, the control current that the shaft 16 resumesmovement and thus 1s reonly flows when the positions of the movablecontact 45 coupled with the driving shaft upon ejection of theopermembers of the position selector and the position switch ative pawl22. do not correspond with one another. The ring 67 is not securedfirmly to the fixed plate 68 In addition, the device shown in Fig. 2 hasa motor but is adapted to turn through a small angle relatively to 1which is controlled automatically, so that switch 46 of this plate. Thestressed springs 63, together with the Fig. 1 is omitted from Fig. 2 andthe electromagnet 49 50 disc 60 and the clamping pawl 66 are thusenabled to operates not only as an actuating magnet for the selectorturn the ring 67 slightly in the direction opposite to the pawl but alsoas a relay. It operates a switch 57 by direction of rotation of theshaft. The movement of means of a make contact connected in series withthe ring 67 and the play in the clamping coupling must, howmotor. Uponthe contact arm 43 being moved into ever, not result in the stud 64being pulled from the a further position not only is the selector pawl40 of pawl 61. There must, therefore, be some back lash in the pawlwheel 41 e ected but also the motor is switched t e co-operation betweenthe stud 64 and the pawl 61 on Immediately the pawl selectors occupy theselected Since this does not fall within the scope of the invenpositionsenergizatton of the magnet 49 ceases, selector tron, and is known 1n theprior art, it will not be given pawl 40 reoccupies its active positionand switch 57 is further consideration.

opened but the motor is not held thereby, since switch 57 60 The strokeof the ring 67 is limited by a. lug 69 enis connected in parallel with aswitch 58 which cooperates gaging a slot 70 in the plate 68. This lughas secured to with the overload coupling 31. Switch 58 is closed so t al member Which CO-OPBIMES h h Wi ch long as the shafts 12 and 16 rotateand is opened when 58- Th movement performed y the g 67 under h shaft 16is locked while shaft 12 still rotates. If even stress of the springs 63upon dlsengagement of the shafts more pawl knobs than those shown inFig. 2 are linked results 111 thls SWltCh belng Upenech up with theshafts 5 and 12, each of them may be It is desirable that the rotaryspeedof the pawl sevided with a switch 58. In this case the motorcontinues lector Should xc ha Of th pawl knob shaft, so to rotate o longas on of th wl k b i till that unless the difference between two lockingpositions mg and its movement does not stop until the last pawl 0f the pw knobs 1S eXCeSSlVelY Small, The selctor has knob shaft is locked andits switch is thus also Opened. taken up its new position before thepawl knob has overload coupling operative to nt l a it h 13 reached itsposition. However, two selected. successive the subject matter of patentapplication Serial No. 51,604 positions of the pawl knob may be in suchclose proxnow Patent No. 2,659,469, issued Nov. 17, 1953, to Unk. imityto one another that a slight release of the springs, One embodiment ofsuch a coupling will be described, by which does not yet cause the pawl61 to engage the way of example, with reference to Fig. 3. This figure75 pawl wheel 59 is sufiicient for the pawl knob to move shows thecoupling pro ected in the axial direction. from one position into theother. In this case the switch The dFlVlIlg S haft Whlch 111 Flgufe 3eXt11dS t0 e n 58 is not closed and hence, on the switch 57 being openedhas seated on it a pawl wheel 59. dlsk 60, which is by the spring 54,the 'motor 1 is not kept actuated by a adapted to while freely about hdriven Shaft, pp current passing through the switch 58. The movement a I61, Whlch engagfis behlmfl 0116 9 teeth f of the motor 1 and hence alsoof the pawl wheel 41 is h p Wheel 50 that the (1150 60 1S carrled alollgthen stopped at an instant when the tooth 53 has not with the pawl 61when the pawl Wheel rotat s 1n the yet contacted selector pawl 40. Thismight give rise to direction indicated by the arrow in Fig. 3.disturbances, such as inadequate penetration of the The disc 60 isunited with a second disc 62 by two pawls. retracting springs 63, ofwhich only one is shown. The 35 Accordingly, according to the invention,the overload coupling 10 is provided, between driving shaft and selectorshaft, with a switch 72 operating in a manner similar to that of theswitch 58 and similarly thereto connected in parallel to switch 57.Switch 72 is closed so long as both the shafts 9 and 73 coupled bycoupling 10 rotate. Consequently, in the event of switch 58 not takingthe function of switch 57 when the latter is opened, this is done byswitch 72. Hence, even in this case the motor continues to rotate untilthe pawl selector shaft is locked, whereupon th; shafts 9 and 73 areseparated with the result that switch 72 is opened.

Even though switch 72 is present, switch 57 cannot be dispensed with,since the former is capable of breaking the circuit but not of startingthe motor. When the pawl selector shaft is unlocked while the shaft 9 isstill stationary, the springs 63 of the overload coupling release andpull the shaft 73 along with them, but the locking member 67 is notsubjected to any force that urges it into the direction of rotation ofthe shaft until the driving shaft together with the pawl wheel 59 startsto rotate. The switch 57 is therefore required to close the circuit ofthe motor.

What we claim is:

1. A shaft positioning device including a pawl knob, said pawl knobcomprising a pawl selector, a locking disc, and a pawl member mounted inoperative relationship with said pawl selector and said locking disc,said pawl selector comprising means for rendering said pawl operative toengage said locking disc in locking relationship therewith in apredetermined position of said pawl selector, undirectional and commondriving means for said pawl selector and said locking disc, an overloadcoupling interposed between said common driving means and said pawlselector, said overload coupling comprising means for completelyseparating said pawl selector from said driving means upon overload andresilient means operable upon such separation to subject said pawlselector to a driving torque, and selectively operable means for lockingsaid pawl selector in said predetermined position.

2. A shaft positioning device including a pawl knob, said pawl knobcomprising a pawl selector mounted on a first shaft, a locking discmounted on a second shaft, a pawl member mounted in operativerelationship with said pawl selector and said locking disc, said pawlselector comprising means for rendering said pawl operative to engagesaid locking disc in locking relationship therewith in a predeterminedposition of said pawl selector, common electric motor driving means forsaid pawl selector and said locking disc, a circuit connected to saidelectric motor means for energizing the same, a switch in said circuit,a separating device interposed between said common driving means andsaid pawl selector for completely separating the connection between saiddriving means and pawl selector upon overload, selectively operablemeans for mechanically locking said pawl selector in said predeterminedposition, and electromagnetic control means controlling both said switchand said selectively operable means for locking said pawl selector.

3. A shaft positioning device including a pawl knob,

said pawl knob comprlsing a pawl selector, 9. locking disc, and a pawlmember mounted in operative relationship with said pawl selector andsaid locking disc, said pawl selector comprising means for renderingsaid pawl operative to engage said locking disc in locking relationshiptherewith in a predetermined position of said pawl selector, commonelectric motor driving means for said pawl selector and said lockingdisc, a circuit connected to said electric motor means for energizingthe same, a first switch in said circuit, an overload couplinginterposed between said common driving means and said pawl selector, asecond overload coupling interposed between said common driving meansand said locking disc, selectively operable means for locking said pawlselector in said predetermined position, and control means for saidswitch, said control means being actuatable by said means for lockingsaid pawl selector, a second switch connected in parallel with saidfirst switch, and means actuated by said second overload coupling forcontrolling said second switch.

4. A shaft positioning device including a pawl knob, said pawl knob compising a pawl selector, a locking disc, and a pawl member mounted inoperative relationship with said pawl selector and said locking disc,said pawl selector comprising means for rendering said pawl operative toengage said locking disc in locking relationship therewith in apredetermined position of said pawl selector, common electric motordriving means for said pawl selector and said locking disc, a circuitconnected to said electric motor means for energizing the same, a firstswitch in said circuit, a first overload coupling interposed betweensaid common driving means and said pawl selector, a second overloadcoupling interposed between said common driving means and said lockingdisc, selectively operable means for locking said pawl selector in saidpredetermined position, and control means for said switch, said controlmeans being actuatable by said means for locking said pawl selector, asecond switch connected in parallel with said first switch, and meansactuated by said second overload coupling for controlling said secondswitch, and a third switch connected in parallel with said first andsecond switches, and means actuated by said first overload coupling forcontrolling said third switch.

5. A shaft positioning device including a pawl knob, said pawl knobcomprising a plurality of pawl selectors and a plurality ofcorresponding locking discs, a plurality of pawl members each mounted inoperative relationship with each pawl selector and corresponding lockingdisc, each pawl selector comprising means for rendering an associatedpawl member operative to engage an associated locking disc in lockingrelationship therewith in a predetermined position of said pawlselector, unidirectional and common driving means for said pawlselectors and said locking discs, an overload coupling interposedbetween said common driving means and said pawl selectors, andselectively operable means for locking said pawl members in a number ofpredetermined positions equal to the number of pawl members, saidselectively operable means comprising a pawl and a pawl wheel, and aposition selector controlling said selectively operable means.

